﻿using System;

namespace demo4
{
    class Program
    {
        static void Main(string[] args)
        {
            //转义字符
            Console.WriteLine("Hello\tWorld\n\n");
            Console.ReadLine();

            const double pi = 3.14159; // 常量声明
            double r;
            Console.WriteLine("Enter Radius: ");
            r = Convert.ToDouble(Console.ReadLine());
            double areaCircle = pi * r * r;
            Console.WriteLine("Radius: {0}, Area: {1}", r, areaCircle);
            Console.ReadLine();
        }
    }
}
